I've seen some say that coming back for his Sr year hurt him:
http://lawlessrepublic.com/2014/02/23/evaluating-cody-hoffmans-results-2014-nfl-combine/" onclick="window.open(this.href);return false;
I don't think it's so clear cut. On the plus side of coming back, he demonstrated consistent productivity over a longer period resulting in school records. That's a real benefit. Yes, his per season numbers dropped, but scouts are paid to understand the why behind trends. And there's plenty of why behind Hoffman's Sr yr drop that isn't related to his abilities. Finally, I don't know that his combine numbers would have been any different after his Jr year. He's the same athlete, and had an injury and shoulder surgery right after his Jr year. That likely would have affected all of his numbers, but especially his vertical jump.